Low-valence Cations Research Articles

Entropy-increased LiMn2O4-based positive electrodes for fast-charging lithium metal batteries

Fast-charging, non-aqueous lithium-based batteries are desired for practical applications. In this regard, LiMn2O4 is considered an appealing positive electrode active material because of its favourable ionic diffusivity due to the presence of three-dimensional Li-ion diffusion channels. However, LiMn2O4 exhibits inadequate rate capabilities and rapid structural degradation at high currents. To circumvent these issues, here we introduce quintuple low-valence cations to increase the entropy of LiMn2O4. As a result, the entropy-increased LiMn2O4-based material, i.e., LiMn1.9Cu0.02Mg0.02Fe0.02Zn0.02Ni0.02O4, when tested in non-aqueous lithium metal coin cell configuration, enable 1000 cell cycles at 1.48 A g−1 (corresponding to a cell charging time of 4 minutes) and 25°C with a discharge capacity retention of about 80%. We demonstrate that the increased entropy in LiMn2O4 leads to an increase in the disordering of dopant cations and a contracted local structure, where the enlarged LiO4 space and enhanced Mn-O covalency improve the Li-ion transport and stabilize the diffusion channels. We also prove that stress caused by cycling at a high cell state of charge is relieved through elastic deformation via a solid-solution transition, thus avoiding structural degradation upon prolonged cycling.

Low-valent cation doping and leaching to construct single-atom Cu decorated Cu-ZnIn2S4 with multiple defects for boosting photocatalytic H2 evolution

It is a promising means to enhance photocatalytic activity by ions doping, single-atom decoration, and vacancies introducing, yet a simple approach to realize their simultaneous appearance in one material remains a great challenge hitherto. Herein, an original strategy of low-valent cation doping and leaching is developed to construct Cu single atom (Cu SAs)-decorated and monovalent Cu ion (Cu+)-doped ZnIn2S4 photocatalyst (RCu-ZIS) with multiple defects. The Cu doping atoms and Cu/In/S vacancies clusters induce electron-poor zones, meanwhile, S vacancies and isolated Cu SAs result in electron-rich regions, thus forming some local electric field with different states of charge, which can act as electron-accepting and donating centers accelerating the transfer and separation of photocarriers. The optimized RCu-ZIS delivers a high visible-light-driven H2 evolution activity of 70.58 mmol·g−1·h−1 with an AQE of 12.24% at 420 nm. This work opens up an all-in-one modification strategy on redounding photocatalytic activity through rational structural fine-tuning.

Tailoring Electronic Structure to Achieve Maximum Utilization of Transition Metal Redox for High-Entropy Na Layered Oxide Cathodes.

Charge compensation from cationic and anionic redox couples accompanying Na+ (de)intercalation in layered oxide cathodes contributes to high specific capacity. However, the engagement level of different redox couples remains unclear and their relationship with Na+ content is less studied. Here we discover that it is possible to take full advantage of the high-voltage transition metal (TM) redox reaction through low-valence cation substitution to tailor the electronic structure, which involves an increased ratio of Na+ content to available charge transfer number of TMs. Taking NaxCu0.11Ni0.11Fe0.3Mn0.48O2 as the example, the Li+ substitution increases the ratio to facilitate the high-voltage TM redox activity, and further F-ion substitution decreases the covalency of the TM-O bond to relieve structural changes. As a consequence, the final high-entropy Na0.95Li0.07Cu0.11Ni0.11Fe0.3Mn0.41O1.97F0.03 cathode demonstrates ∼29% capacity increase contributed by the high-voltage TMs and exhibits excellent long-term cycling stability due to the improved structural reversibility. This work provides a paradigm for the design of high-energy-density electrodes by simultaneous electronic and crystal structure modulation.

Homovalent cationic Se dopant with noble metal-like activation properties to enhance the sensitivity of SnO2 sensors

A challenge for low-valence cation doping in SnO2 materials is that the sharply elevated baseline resistance is detrimental to sensor stability and the subsequent signal acquisition. In contrast, Homovalent doping has little effect on resistance but the effective homovalent dopant is few. Herein, we find the non-metallic element Se is prone to form cationic SeSn defects in SnO2, which can improve the sensitivity of the SnO2-based sensors with a moderate rise in baseline resistance. The homovalent Se doping make the species and ratio of adsorbed oxygen on Se-doped SnO2 surface basically unchanged after doping. Further experiments and theoretical calculations confirm the sensitization mechanism of Se-doped SnO2 can be attributed to the higher activity of adsorbed oxygen on its surface. Therefore, the sensor based on Se-doped SnO2 can have sufficient sensing-reactions and charge transfer at a temperature close to the maximum value of the baseline resistance, which makes the sensor better to sensitize the target gases requiring high temperature for sensing-reactions. This noble metal-like activation behavior of Se dopant is derived from the easier breaking of Se-O bond compared to Sn-O bond during CO oxidation which provides a new basis for the selection of dopants from the perspective of bond energy.

The effect of a biofilm-forming bacterium Tenacibaculum mesophilum D-6 on the passive film of stainless steel in the marine environment

The microbiologically influenced corrosion of 304 stainless steel in the presence of a marine biofilm-forming bacterium Tenacibaculum mesophilum D-6 was systematically investigated by means of electrochemical techniques and surface analyses to reveal the effect of the selective attachment and adsorption of the biofilms on the passivity breakdown of the stainless steel. It was found that the T. mesophilum D-6 was electroactive and could oxidize low valent cations and metal, facilitating the local dissolution of the passive film and the substrate in the film defects, nearly doubling the surface roughness. The biofilms of T. mesophilum D-6 with mucopolysaccharide secreta and chloride ions tended to preferentially adsorb at the defects of the passive film on the steel, yielding non-homogeneous microbial aggregates and local Cl− enrichment there. The adsorption of the bacteria and chloride ions reduced the thickness of passive film by 23.9%, and generate more active sites for pitting corrosion on the passive film and more semiconducting carrier acceptors in the film. The maximum current density of the 304 SS in the presence of T. mesophilum D-6 was over one order of magnitude higher than that in the sterile medium, and the largest pit was deepened 3 times.

Hydridotetrylene [Ar*EH] (E = Ge, Sn, Pb) coordination at tantalum, tungsten, and zirconium.

In a reaction of tantalocene trihydride with the low valent aryl tin cation [Ar*Sn(C6H6)][Al(OC{CF3}3)4] (1a) the hydridostannylene complex [Cp2TaH2–Sn(H)Ar*][Al(OC{CF3}3)4] (2) was synthesized. Hydride bridged adducts [Cp2WH2EAr*][Al(OC{CF3}3)4] (E = Sn 3a, Pb 3b) were isolated as products of the reaction between Cp2WH2 and cations [Ar*E(C6H6)][Al(OC{CF3}3)4] (E = Sn 1a, Pb 1b). The tin adduct 3a exhibits a proton migration to give the hydridostannylene complex [Cp2W(H) Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Sn(H)Ar*][Al(OC{CF3}3)4] 4a. The cationic complex 4a is deprotonated at the tin atom in reaction with base MeNHC at 80 °C to give a hydrido-tungstenostannylene [Cp2W(H)SnAr*] 5a. Reprotonation of metallostannylene 5a with acid [H(Et2O)2][BArF] provides an alternative route to hydridotetrylene coordination. Complex 4a adds hydride to give the dihydrostannyl complex [Cp2W(H)–SnH2Ar*] (7). With styrene 4a shows formation of a hydrostannylation product [Cp2W(H)Sn(CH2CH2Ph)Ar*][Al(OC{CF3}3)4] (8). The lead adduct 3b was deprotonated with MeNHC to give plumbylene 5b [Cp2W(H)PbAr*]. Protonation of 5b with [H(Et2O)2][Al(OC{CF3}3)4] at −40 °C followed by low temperature NMR spectroscopy indicates a hydridoplumbylene intermediate [Cp2W(H)Pb(H)Ar*]+ (4b). Hydrido-tungstenotetrylenes of elements Ge (5c), Sn (5a) and Pb (5b) were also synthesized reacting the salt [Cp2W(H)Li]4 with organotetrylene halides. The metallogermylene [Cp2W(H)GeAr*] (5c) shows an isomerization via 1,2-H-migration to give the hydridogermylene [Cp2WGe(H)Ar*] (9), which is accelerated by addition of AIBN. 9 is at rt photochemically transferred back to 5c under light of a mercury vapor lamp. Zirconocene dihydride [Cp2ZrH2]2 reacts with tin cation 1a to give the trinuclear hydridostannylene adduct 10 [({Cp2Zr}2{μ-H})(μ-H)2μ-Sn(H)Ar*][Al(OC{CF3}3)4]. Deprotonation of 10 was carried out using benzyl potassium to give neutral [({Cp2Zr}2{μ-H})(μ-H)μ-Sn(H)Ar*] (11). 11 was also obtained from the reaction of low valent tin hydride [Ar*SnH]2 with two equivalents of [Cp2ZrH2]2. The trihydride Ar*SnH3 reacts with half of an equivalent of [Cp2ZrH2]2 under evolution of hydrogen and formation of a dihydrostannyl complex 13 [Cp2Zr(μ-H)SnH2Ar*]2 and with further equivalents of Ar*SnH3 to give bis(hydridostannylene) complex [Cp2Zr{Sn(H)Ar*}2].

From mixed group 13 cations [M(AlCp*)3]+ (M = Ga/In/Tl) to an Al4 + cluster.

AlCp*-complexes with transition metals have shown to be highly reactive and enable C-H or Si-H bond activation. Yet, complexes of AlCp* with low-valent main-group metals are scarce. Here, we report the syntheses of [M(AlCp*)3][Al(ORF)4] (RF = C(CF3)3) with M = Ga, In, Tl, which include the first covalent Al-In and Al-Tl bonds. For M = Ga, AlCp*-coordination induced the formation of the dication [Ga2(AlCp*)6]2+ in the solid state, which exhibits a solvent and temperature dependent monomer-dimer equilibrium in solution. By contrast, the In and Tl complexes are monomeric and prone to reduction to the metal by the electron-rich AlCp*-moieties. The QTAIM analysis suggests that the metal centres are already highly reduced in the complexes, while the positive charge is distributed onto the AlCp* units. Addition of Me3TACN (1,4,7-trimethyl-1,4,7-triazacyclononane) to the Ga- and Tl-complex salts resulted in an isomerization to the novel low-valent Al4 + cation [(Me3TACN)Al(AlCp*)3][Al(ORF)4]. Intermittently formed tetrahedral GaAl3 + clusters could be structurally characterized. From a detailed mechanistic study of this isomerization, the very high yield and clean preparation of [(Me3TACN)Al(AlCp*)3][Al(ORF)4] was devised from [M(Me3TACN)][Al(ORF)4] (M = Ga, Tl) and [(AlCp*)4].

Influence of the charge compensation effect on the metal–insulator transition of Mg-W co-doped VO2

Cation co-doping was proved an effective approach to reduce the metal–insulator transition (MIT) temperature (θc) of vanadium dioxide (VO2) for realizing excellent optical switching properties near room temperature, but its mechanism is remaining a great challenge. Herein, the Mg-W co-doped VO2 films are fabricated through hydrothermal growth. By changing the Mg content with maintaining 1 at% W doping level, it is observed that Mg dopants raise the θc of co-doped VO2 at a rate of ∼ 22 ℃ per at% Mg as the Mg content is less than ∼ 1 at%, but loses efficacy more than 1 at% Mg. The resistance of the co-doped VO2 films show the similar variation trend. The valence-band XPS spectra indicate that the Mg dopants counteract the VBE uplifting of VO2 caused by W dopants, consequently enlarging the optical band gap of W-doped VO2, which would partially explain the improvement of the visible light transmittance of W-doped VO2 induced by Mg dopants. The results clearly evidence that the charge compensation takes effect in the co-doped VO2, demonstrating the co-doping of high- and low-valent cations is unfavorable for effectively decreasing θc of VO2, and reveal the electron doping plays a key role in reducing θc.

Controlling the carrier density in niobium oxynitride BaNbO2N via cation doping for efficient photoelectrochemical water splitting under visible light

Lower-valent cation doping enables appropriate reduction of undesirably high donor density in BaNbO2N, providing both a suitable electron conductivity and hole diffusion length with high photoelectrochemical performance for water splitting.

Saranovskite, SrCaFe2+2(Cr4Ti2)Ti12O38, a new crichtonite-group mineral

The new crichtonite-group mineral saranovskite, ideally SrCaFe2+2(Cr4Ti2)Ti12O38, was discovered in the Glavnoe Saranovskoe deposit, Middle Urals, Russia, and named after the type locality. The associated minerals are chromite, Cr-bearing clinochlore, and calcite. Saranovskite forms black crude equant crystals about 2 mm across. The lustre is submetallic, and the streak is brownish-gray. Cleavage is not observed. The Mohs hardness is 6. Density calculated using the empirical formula is equal to 4.501 g cm–3. The reflectance spectra in visible range are given. The IR spectrum shows the absence of H-, B- and C-bearing groups. The Raman spectrum of saranovskite confirms the absence of H-bearing groups and indicates a rather high degree of ordering of Ti4+ and lower-valence cations. The chemical composition of saranovskite is (wt.%; electron microprobe, total iron apportioned between FeO and Fe2O3 taking into account charge balance): MgO 2.01, CaO 1.43, MnO 0.21, FeO 8.14, SrO 3.27, BaO 2.18, Al2O3 0.53, Sc2O3 0.69, Cr2O3 10.27, Fe2O3 2.19, Y2O3 1.56, La2O3 0.94, Ce2O3 0.91, Pr2O3 0.14, Nd2O3 0.35, TiO2 64.25, ZrO2 0.58, total 99.65. The crystal chemical formula of saranovskite is (Sr0.55Ba0.25Ln0.10Ca0.10)(Ca0.36Y0.25Ln0.16Fe2+0.08Zr0.10Mn0.05) (Fe2+1.12Mg0.88)(Cr3+2.34Ti2.28Fe2+0.91Fe3+0.11Al0.18Sc3+0.18)(Ti5.82Fe3+0.18)Ti6.0O38. The idealized formula is SrCaFe2+2(Cr4Ti2)Ti12O38. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.0243. The new mineral is isostructural to other crichtonite-group members. Saranovskite is trigonal, space group R $$\overline{3}$$ , with a = 10.3553(2) A, c = 20.7301(4) A, V = 1925.12(8) A3 and Z = 3. The strongest lines of the powder X-ray diffraction pattern [d, A (I, %) (hkl)] are: 3.398 (75) (024), 2.881 (100) (– 126), 2.842 (65) (– 234), 2.247 (67) (– 144). 2.137 (76) (– 345), 1.799 (63) (– 348), 1.597 (72) (– 1.4.10, 152), 1.439 (76) (520).

Suppression of Nb reduction in high-κ perovskite oxynitrides, BaMxNb1−xO2+4xN1−4x (M = Li, Na; x ≤ 0.15)

Dielectric polarization of the Nb-containing perovskite oxynitrides was realized through the controls of the electronic and geometric environments of Nb. To suppress the Nb reduction which is detrimental to the dielectric polarization, two different approaches were employed, particularly in the preparation of BaNbO2N. First, the starting reactants were provided with an excess of Ba, to avoid the possibility of surplus Nb. Second, part of Nb was replaced with low-valence cations, to form BaMxNb1−xO2+4xN1−4x (M = Li, Na; x ≤ 0.15). Diffuse-reflectance spectroscopy and X-ray photoelectron spectroscopy indicated that the introduction of M+ is effective in preserving the Nb5+ state. As revealed by the Fourier-transform infrared spectroscopy, the octahedral frameworks of BaNbO2N and BaMxNb1−xO2+4xN1−4x were substantially distorted, to form readily polarizable lattices. The dielectric constant (κ) of BaNa0.11Nb0.89O2.44N0.56 was evaluated to be as high as 15,000 at 300 K.

Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 ≤ x ≤ 1) solid solution

Fluorite-derived A2B2O7 and ABC2O7 structures, i.e. pyrochlore and zirconolite, are promising ceramic matrices for high-level radioactive waste immobilization, especially for minor actinides. Though substitutions of low valent cations were reported by many studies, fewer researches were carried out on the incorporation of high valency elements on these fluorite-derived matrices. In this study, a series of CaZr1-xNdxTi2-xNbxO7 (x = 0.05–1.0) ceramics was investigated to unravel the effect of Nb5+ - one of the main impurities in natural zirconolite, on the evolutions of crystal structure, substitution mechanism and phase transformation. X-ray photoelectron spectroscopy was used to confirm the existence of Nb5+ in the samples. Fluorite-derived structures (zirconolite-2M, 3T, 4 M and pyrochlore) with increasing Nb5+ contents simultaneously appeared as single-phase or multi-phase assemblages in the matrices, revealed by the combination of synchrotron X-ray diffraction and scanning electron microscopy-energy dispersive x-ray spectroscopy. Almost single-phase zirconolite-2M and pyrochlore were observed only in the ranges of 0.05 ≤ x ≤ 0.1 and 0.5 ≤ x ≤ 0.9, respectively. Rietveld structural analysis of the zirconolite-2M phase showed that Nd3+ ions preferably occupied the Zr sites while Nb5+ ions substituted the Ti sites. This result is different from the mechanisms reported in the literature when lower valency (≤+3) was as charge compensator or there was no charge compensator in the REE doped zirconolite (REE = rare earth element). In the pyrochlore structure, the Ca2+, Nd3+ and Zr4+ ions occupied the A sublattice while Ti4+ and Nb5+ ions filled in the B sublattice, and there is charge compensation between A and B sublattices. The results in this study showed a different charge compensation mechanism of the fluorite-derived structures when higher valency elements incorporate into the lattice and will be very helpful for high-level radioactive waste immobilization.

Investigation on the oxide-oxide galvanic displacement reactions employed in the preparation of electrocatalytic layers

Galvanic displacement reactions between sacrificial oxide layers and metal cations, leading to the formation of secondary oxide layers, have been studied with the aim of collecting new experimental evidence on their mechanism. The study has been carried out by combining electrochemical methods, SEM-EDS and XPS depth profiling. Both porous and compact PbO2 layers have been used as sacrificial oxides and reacted, in different experiments, with: (i) a single low-valent cation, (ii) two cations in sequential exchange reactions or (iii) two cations simultaneously. The experimental results converged to show (i) a lack of correlation between the reaction driving force and the secondary oxide growth rate, (ii) the incorporation of cations from solution at the secondary oxide/electrolyte interface, (iii) the transport of Pb species through the growing secondary oxide layer and (iv) a major effect of mass transport on the growth rate.

Revealing High Na-Content P2-Type Layered Oxides as Advanced Sodium-Ion Cathodes.

Layered Na-based oxides with the general composition of NaxTMO2 (TM: transition metal) have attracted significant attention for their high compositional diversity that provides tunable electrochemical performance for electrodes in sodium-ion batteries. The various compositions bring forward complex structural chemistry that is decisive for the layered stacking structure, Na-ion conductivity, and the redox activity, potentially promising new avenues in functional material properties. In this work, we have explored the maximum Na content in P2-type layered oxides and discovered that the high-content Na in the host enhances the structural stability; moreover, it promotes the oxidation of low-valent cations to their high oxidation states (in this case Ni2+). This can be rationalized by the increased hybridization of the O(2p)-TM(3d-eg*) states, affecting both the local TM environment as well as the interactions between the NaO2 and TMO2 layers. These properties are highly beneficial for the Na storage capabilities as required for cathode materials in sodium-ion batteries. It leads to excellent Na-ion mobility, a large storage capacity (>100 mAh g–1 between 2.0-4.0 V), yet preventing the detrimental sliding of the TMO2 layers (P2–O2 structural transition), as reflected by the ultralong cycle life (3000 (dis)charge cycles demonstrated). These findings expand the horizons of high Na-content P2-type materials, providing new insights of the electronic and structural chemistry for advanced cathode materials.

Effect of Nb–Sm co-doping on the ionic conductivity of Li7La3Zr2O12 electrolytes

Li-conducting oxide material Li7La3Zr2O12 is a promising solid electrolyte due to its relatively high conductivity. In this work, Li7−x+yLa3Zr2−x−yNbxSmyO12 (0 ≤ x ≤ 0.4, 0 ≤ y ≤ 0.1) was prepared using a solid-state synthesis method, and the effects of Nb–Sm co-doping on the structure, microstructure, and conductivity of Li7La3Zr2O12 were investigated. Results showed that the co-doping of supervalent cation Nb and low-valent cation Sm was able to facilitate the formation of cubic garnet modification. The optimized composition Li6.7La3Zr1.5Nb0.4Sm0.1O12 showed the highest relative density at 94.3%, and reached the highest total conductivity of 1.06 × 10−3 S/cm at 30 °C, with the lowest activation energy of 0.39 eV. Based on SEM and above results, it can be found that the Nb–Sm co-doping can enhance sinterability and increase density, leading to lower impedance and higher conductivity. Although a small amount of impurity phase LaNbO4 was observed in the XRD patterns, its overall influence on ionic conductivity was negligible.

Enhanced photovoltaic properties of gradient calcium-doped BiFeO3 films

The photovoltaic properties of ferroelectric films have been extensively studied due to their potential applications in the fields of photodetection, energy conversion harvesting and storage. However, the effect of the gradient distribution of oxygen vacancies on the photovoltaic properties remains unclear. Herein, we prepared BiFeO3 (BFO) and two types of gradient calcium-doped BiFeO3 (BiFeO3/Bi0.95Ca0.05FeO2.975/Bi0.90Ca0.10FeO2.950/Bi0.85Ca0.15FeO2.925: BCFO-1 and Bi0.85Ca0.15FeO2.925/Bi0.90Ca0.10FeO2.950/Bi0.95Ca0.05FeO2.975/BiFeO3: BCFO-2) films deposited on fluorine-doped tin oxide glass substrates. Piezoresponse force microscopy studies indicate the upward self-polarization phenomenon in BFO and BCFO-1 films, while the downward self-polarization phenomenon in BCFO-2 films. The J–V characteristic curves show rectifier behaviors for these films due to the configuration of oxygen vacancies. For photovoltaic response, the open circuit voltage of BCFO-1 films is more than 2 times higher than that of BFO films, and the short-circuit photocurrent densities of BCFO-1 and BCFO-2 films are increased by nearly 32 and 6 times, respectively. The direction and magnitude of photovoltaic response are possibly associated with the energy band modulation governed by self-polarization and the gradient distribution of oxygen vacancies. The work demonstrates the merits of gradient doping with lower valence cation towards enhanced photovoltaic properties with high stability for ferroelectric oxides.

Fabrication and scintillation properties of Pr:Lu3Al5O12 transparent ceramics from co-precipitated nanopowders

Sintering aids may seriously deteriorate the luminescence properties of the ceramics especially for scintillators. In this work, 0.25 at%Pr:Lu3Al5O12 transparent ceramics were prepared from the co-precipitated nanopowders without any sintering aids. Ammonium hydrogen carbonate was used as precipitant and the influences of precipitant to metal ions molar ratio on nanopowders and ceramics were investigated. Excessive or insufficient precipitant will worsen the phase-purity and dispersity of the nanopowders. The nonuniform dissolution of the Lu and Al precipitants in the titration and washing process, which results in the nonstoichiometry of Al excess in the ceramics and deteriorates the optical quality. After optimizing the ratio of Lu/Al in raw powders, Pr:Lu3Al5O12 ceramics with the in-line transmittance above 80% in the visible band were obtained. The light yield is 7086 Ph/MeV and the energy resolution is 16.9% which is inferior to that of the good Pr:Lu3Al5O12 crystal. The low valent cation impurities in the raw material increase the concentration of Pr4+ and diminish the light yield.

Comparative Study on Removal of NOx and Soot with A-site Substituted La2NiO4 Perovskite-like by Different Valence Cation

La1.8M0.2NiO4 (M = Na+, Sr2+, Ce3+) perovskite-like catalysts were prepared by citric acid complexation method. XRD, BET, FT-IR, SEM, XPS, H2-TPR, O2-TPD, MS-Soot-TPR, MS-NO-TPD and catalytic activity measurements were carried out to investigate the effect of A-site substitution on structure and catalytic performance for simultaneous removal soot and NOx. The characterization results show that La1.8M0.2NiO4 catalyst has high concentration of oxygen vacancies, more surface active oxygen, more trivalent nickel ions and better reducibility, which determines its better catalytic performance. The introduction of low valence cations at the A site significantly reduces the characteristic combustion temperature of soot and effectively promotes the reduction of NOx by soot. La1.8Sr0.2NiO4 catalyst exhibited the best soot removal performance with Ti 331 °C and Tm 473 °C, while La1.8Na0.2NiO4 catalyst showed the highest NOx conversion of 90%. Based on in situ DRIFTS and other characterization results, a possible mechanism for simultaneous removal of NOx and soot was proposed.

Modification of optical and electrical properties of nanocrystalline VO2·0.5 H2O/ZrV2O7: influence of Cs, Cr and Ga doping

A facile and economical route has been demonstrated for large-scale synthesis of nano VO2·0.5 H2O/ZrV2O7 and it is doping with Cs, Cr and Ga using combined precipitation-hydrothermal that followed by a gentle heating at low temperature. The growth mechanism of doping is discussed and investigated by XRD, SEM, TEM, Raman, TGA, DSC, and UV–vis spectroscopy. The band gap is enhanced with doping. The results show that the all composites have a negative thermal coefficient in the range 25–100°C while it has a positive thermal coefficient in the range 100–300°C. Also, Cs doped has increase in conductivity as compared to Cr doped which may be due to the enhancement of oxygen vacancies as resulted from addition of low valence cations. Doping with Cr or Cs show the contribution of grain and grain boundary properties, respectively, while the doping with Ga shows the insulating behavior.

Electrochemical behaviors and passive film properties of Fe-based bulk metallic glass in Cl−-containing acetic acid solutions under high temperature

This study aimed to investigate the electrochemical behavior and passive film properties of Fe-based bulk metallic glass (BMG) formed in Cl−-containing acetic acid solutions under high temperature. Electrochemical tests showed that Fe-based BMG exhibited excellent pitting resistance and stable passivation characteristics. However, the uniform corrosion resistance of Fe-based BMG is deteriorated in the presence of Cl− anions. Mott-Schottky, X-ray photoelectron spectroscopy depth profiling, and ultra-violet photoelectron spectroscopy analyses revealed that the passive films possess a duplex membrane structure. High-valence cations and Cl− anions relatively localized in the external layer, whereas low-valence cations relatively localized in the internal layer. Moreover, Cl− exposure increases the porosity and decreases the compactness of the passive film by modifying stoichiometry, improving acceptor density, reducing work function, and enhancing the state density of valence electrons around the Fermi level. Results implied that Fe-based BMGs are potential substitutes for conventional stainless steel components that are exposed to organic manufacturing environments.